CD8A and bacterial urinary tract infection: Higher cellular immune competence, particularly CD8 + T-cell counts and higher IFN-γ/IL-4 ratio in functional T-cell assays, were associated with a lower UTI risk (HR [95% CI] per log-transformed unit: CD8 + T-cells 0.34 [0.18—0.65], IFN-γ/IL-4 ratio 0.53 [0.33–0.83]).